yamllint version 1.30.0

According to the YAML specification [^1]:

- > It is an error for an alias node to use an anchor that does not
  > previously occur in the document.

  The `forbid-undeclared-aliases` option checks that aliases do have a
  matching anchor declared previously in the document. Since this is
  required by the YAML spec, this option is enabled by default.

- > The alias refers to the most recent preceding node having the same
  > anchor.

  This means that having a same anchor repeated in a document is
  allowed. However users could want to avoid this, so the new option
  `forbid-duplicated-anchors` allows that. It's disabled by default.

- > It is not an error to specify an anchor that is not used by any
  > alias node.

  This means that it's OK to declare anchors but don't have any alias
  referencing them. However users could want to avoid this, so a new
  option (e.g. `forbid-unused-anchors`) could be implemented in the
  future. See https://github.com/adrienverge/yamllint/pull/537.

Fixes #395
Closes #420

[^1]: https://yaml.org/spec/1.2.2/#71-alias-nodes

CHANGELOG.rst

@@ -1,6 +1,15 @@
 Changelog
 =========
 
+1.30.0 (2023-03-22)
+-------------------
+
+- Rule ``anchors``: add new rule to detect undeclared or duplicated anchors
+- Python API: prevent using ``is_file_ignored()`` with null ``filepath``
+- Docs: fix misleading Python API example
+- Docs: fix plain text code snippet example
+- Docs: update pre-commit hook example
+
 1.29.0 (2023-01-10)
 -------------------
 

docs/development.rst

@@ -11,7 +11,7 @@ Basic example of running the linter from Python:
    import yamllint
 
    yaml_config = yamllint.config.YamlLintConfig("extends: default")
-   for p in yamllint.linter.run("example.yaml", yaml_config):
+   for p in yamllint.linter.run(open("example.yaml", "r"), yaml_config):
        print(p.desc, p.line, p.rule)
 
 .. automodule:: yamllint.linter

docs/disable_with_comments.rst

@@ -117,7 +117,7 @@ post-template processing).
 Example of a Jinja2 code that cannot be parsed as YAML because it contains
 invalid tokens ``{%`` and ``%}``:
 
-.. code-block::
+.. code-block:: text
 
  # This file IS NOT valid YAML and will produce syntax errors
  {% if extra_info %}

docs/integration.rst

@@ -4,7 +4,7 @@ Integration with other software
 Integration with pre-commit
 ---------------------------
 
-You can integrate yamllint in `pre-commit <http://pre-commit.com/>`_ tool.
+You can integrate yamllint in the `pre-commit <https://pre-commit.com/>`_ tool.
 Here is an example, to add in your .pre-commit-config.yaml
 
 .. code:: yaml
@@ -12,11 +12,13 @@ Here is an example, to add in your .pre-commit-config.yaml
   ---
   # Update the rev variable with the release version that you want, from the yamllint repo
   # You can pass your custom .yamllint with args attribute.
-  - repo: https://github.com/adrienverge/yamllint.git
-    rev: v1.17.0
-    hooks:
-      - id: yamllint
-        args: [-c=/path/to/.yamllint]
+  repos:
+    - repo: https://github.com/adrienverge/yamllint.git
+      rev: v1.29.0
+      hooks:
+        - id: yamllint
+          args: [--strict, -c=/path/to/.yamllint]
+
 
 Integration with GitHub Actions
 -------------------------------

docs/rules.rst

@@ -14,6 +14,11 @@ This page describes the rules and their options.
    :local:
    :depth: 1
 
+anchors
+-------
+
+.. automodule:: yamllint.rules.anchors
+
 braces
 ------
 

tests/rules/test_anchors.py

@@ -0,0 +1,209 @@
+# Copyright (C) 2023 Adrien Vergé
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+from tests.common import RuleTestCase
+
+
+class AnchorsTestCase(RuleTestCase):
+    rule_id = 'anchors'
+
+    def test_disabled(self):
+        conf = 'anchors: disable'
+        self.check('---\n'
+                   '- &b true\n'
+                   '- &i 42\n'
+                   '- &s hello\n'
+                   '- &f_m {k: v}\n'
+                   '- &f_s [1, 2]\n'
+                   '- *b\n'
+                   '- *i\n'
+                   '- *s\n'
+                   '- *f_m\n'
+                   '- *f_s\n'
+                   '---\n'  # redeclare anchors in a new document
+                   '- &b true\n'
+                   '- &i 42\n'
+                   '- &s hello\n'
+                   '- *b\n'
+                   '- *i\n'
+                   '- *s\n'
+                   '---\n'
+                   'block mapping: &b_m\n'
+                   '  key: value\n'
+                   'extended:\n'
+                   '  <<: *b_m\n'
+                   '  foo: bar\n'
+                   '---\n'
+                   '{a: 1, &x b: 2, c: &y 3, *x: 4, e: *y}\n'
+                   '...\n', conf)
+        self.check('---\n'
+                   '- &i 42\n'
+                   '---\n'
+                   '- &b true\n'
+                   '- &b true\n'
+                   '- &b true\n'
+                   '- &s hello\n'
+                   '- *b\n'
+                   '- *i\n'    # declared in a previous document
+                   '- *f_m\n'  # never declared
+                   '- *f_m\n'
+                   '- *f_m\n'
+                   '- *f_s\n'  # declared after
+                   '- &f_s [1, 2]\n'
+                   '---\n'
+                   'block mapping: &b_m\n'
+                   '  key: value\n'
+                   '---\n'
+                   'block mapping 1: &b_m_bis\n'
+                   '  key: value\n'
+                   'block mapping 2: &b_m_bis\n'
+                   '  key: value\n'
+                   'extended:\n'
+                   '  <<: *b_m\n'
+                   '  foo: bar\n'
+                   '---\n'
+                   '{a: 1, &x b: 2, c: &x 3, *x: 4, e: *y}\n'
+                   '...\n', conf)
+
+    def test_forbid_undeclared_aliases(self):
+        conf = ('anchors:\n'
+                '  forbid-undeclared-aliases: true\n'
+                '  forbid-duplicated-anchors: false\n')
+        self.check('---\n'
+                   '- &b true\n'
+                   '- &i 42\n'
+                   '- &s hello\n'
+                   '- &f_m {k: v}\n'
+                   '- &f_s [1, 2]\n'
+                   '- *b\n'
+                   '- *i\n'
+                   '- *s\n'
+                   '- *f_m\n'
+                   '- *f_s\n'
+                   '---\n'  # redeclare anchors in a new document
+                   '- &b true\n'
+                   '- &i 42\n'
+                   '- &s hello\n'
+                   '- *b\n'
+                   '- *i\n'
+                   '- *s\n'
+                   '---\n'
+                   'block mapping: &b_m\n'
+                   '  key: value\n'
+                   'extended:\n'
+                   '  <<: *b_m\n'
+                   '  foo: bar\n'
+                   '---\n'
+                   '{a: 1, &x b: 2, c: &y 3, *x: 4, e: *y}\n'
+                   '...\n', conf)
+        self.check('---\n'
+                   '- &i 42\n'
+                   '---\n'
+                   '- &b true\n'
+                   '- &b true\n'
+                   '- &b true\n'
+                   '- &s hello\n'
+                   '- *b\n'
+                   '- *i\n'    # declared in a previous document
+                   '- *f_m\n'  # never declared
+                   '- *f_m\n'
+                   '- *f_m\n'
+                   '- *f_s\n'  # declared after
+                   '- &f_s [1, 2]\n'
+                   '---\n'
+                   'block mapping: &b_m\n'
+                   '  key: value\n'
+                   '---\n'
+                   'block mapping 1: &b_m_bis\n'
+                   '  key: value\n'
+                   'block mapping 2: &b_m_bis\n'
+                   '  key: value\n'
+                   'extended:\n'
+                   '  <<: *b_m\n'
+                   '  foo: bar\n'
+                   '---\n'
+                   '{a: 1, &x b: 2, c: &x 3, *x: 4, e: *y}\n'
+                   '...\n', conf,
+                   problem1=(9, 3),
+                   problem2=(10, 3),
+                   problem3=(11, 3),
+                   problem4=(12, 3),
+                   problem5=(13, 3),
+                   problem6=(24, 7),
+                   problem7=(27, 36))
+
+    def test_forbid_duplicated_anchors(self):
+        conf = ('anchors:\n'
+                '  forbid-undeclared-aliases: false\n'
+                '  forbid-duplicated-anchors: true\n')
+        self.check('---\n'
+                   '- &b true\n'
+                   '- &i 42\n'
+                   '- &s hello\n'
+                   '- &f_m {k: v}\n'
+                   '- &f_s [1, 2]\n'
+                   '- *b\n'
+                   '- *i\n'
+                   '- *s\n'
+                   '- *f_m\n'
+                   '- *f_s\n'
+                   '---\n'  # redeclare anchors in a new document
+                   '- &b true\n'
+                   '- &i 42\n'
+                   '- &s hello\n'
+                   '- *b\n'
+                   '- *i\n'
+                   '- *s\n'
+                   '---\n'
+                   'block mapping: &b_m\n'
+                   '  key: value\n'
+                   'extended:\n'
+                   '  <<: *b_m\n'
+                   '  foo: bar\n'
+                   '---\n'
+                   '{a: 1, &x b: 2, c: &y 3, *x: 4, e: *y}\n'
+                   '...\n', conf)
+        self.check('---\n'
+                   '- &i 42\n'
+                   '---\n'
+                   '- &b true\n'
+                   '- &b true\n'
+                   '- &b true\n'
+                   '- &s hello\n'
+                   '- *b\n'
+                   '- *i\n'    # declared in a previous document
+                   '- *f_m\n'  # never declared
+                   '- *f_m\n'
+                   '- *f_m\n'
+                   '- *f_s\n'  # declared after
+                   '- &f_s [1, 2]\n'
+                   '---\n'
+                   'block mapping: &b_m\n'
+                   '  key: value\n'
+                   '---\n'
+                   'block mapping 1: &b_m_bis\n'
+                   '  key: value\n'
+                   'block mapping 2: &b_m_bis\n'
+                   '  key: value\n'
+                   'extended:\n'
+                   '  <<: *b_m\n'
+                   '  foo: bar\n'
+                   '---\n'
+                   '{a: 1, &x b: 2, c: &x 3, *x: 4, e: *y}\n'
+                   '...\n', conf,
+                   problem1=(5, 3),
+                   problem2=(6, 3),
+                   problem3=(21, 18),
+                   problem4=(27, 20))

yamllint/__init__.py

@@ -21,7 +21,7 @@ indentation, etc."""
 
 
 APP_NAME = 'yamllint'
-APP_VERSION = '1.29.0'
+APP_VERSION = '1.30.0'
 APP_DESCRIPTION = __doc__
 
 __author__ = 'Adrien Vergé'

yamllint/conf/default.yaml

@@ -6,6 +6,7 @@ yaml-files:
   - '.yamllint'
 
 rules:
+  anchors: enable
   braces: enable
   brackets: enable
   colons: enable

yamllint/linter.py

@@ -223,7 +223,7 @@ def run(input, conf, filepath=None):
     :param input: buffer, string or stream to read from
     :param conf: yamllint configuration object
     """
-    if conf.is_file_ignored(filepath):
+    if filepath is not None and conf.is_file_ignored(filepath):
         return ()
 
     if isinstance(input, (bytes, str)):

yamllint/rules/__init__.py

@@ -14,6 +14,7 @@
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 from yamllint.rules import (
+    anchors,
     braces,
     brackets,
     colons,
@@ -39,6 +40,7 @@ from yamllint.rules import (
 )
 
 _RULES = {
+    anchors.ID: anchors,
     braces.ID: braces,
     brackets.ID: brackets,
     colons.ID: colons,

yamllint/rules/anchors.py

@@ -0,0 +1,118 @@
+# Copyright (C) 2023 Adrien Vergé
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+"""
+Use this rule to report duplicated anchors and aliases referencing undeclared
+anchors.
+
+.. rubric:: Options
+
+* Set ``forbid-undeclared-aliases`` to ``true`` to avoid aliases that reference
+  an anchor that hasn't been declared (either not declared at all, or declared
+  later in the document).
+* Set ``forbid-duplicated-anchors`` to ``true`` to avoid duplications of a same
+  anchor.
+
+.. rubric:: Default values (when enabled)
+
+.. code-block:: yaml
+
+ rules:
+   anchors:
+     forbid-undeclared-aliases: true
+     forbid-duplicated-anchors: false
+
+.. rubric:: Examples
+
+#. With ``anchors: {forbid-undeclared-aliases: true}``
+
+   the following code snippet would **PASS**:
+   ::
+
+    ---
+    - &anchor
+      foo: bar
+    - *anchor
+
+   the following code snippet would **FAIL**:
+   ::
+
+    ---
+    - &anchor
+      foo: bar
+    - *unknown
+
+   the following code snippet would **FAIL**:
+   ::
+
+    ---
+    - &anchor
+      foo: bar
+    - <<: *unknown
+      extra: value
+
+#. With ``anchors: {forbid-duplicated-anchors: true}``
+
+   the following code snippet would **PASS**:
+   ::
+
+    ---
+    - &anchor1 Foo Bar
+    - &anchor2 [item 1, item 2]
+
+   the following code snippet would **FAIL**:
+   ::
+
+    ---
+    - &anchor Foo Bar
+    - &anchor [item 1, item 2]
+"""
+
+
+import yaml
+
+from yamllint.linter import LintProblem
+
+
+ID = 'anchors'
+TYPE = 'token'
+CONF = {'forbid-undeclared-aliases': bool,
+        'forbid-duplicated-anchors': bool}
+DEFAULT = {'forbid-undeclared-aliases': True,
+           'forbid-duplicated-anchors': False}
+
+
+def check(conf, token, prev, next, nextnext, context):
+    if conf['forbid-undeclared-aliases'] or conf['forbid-duplicated-anchors']:
+        if isinstance(token, (yaml.StreamStartToken, yaml.DocumentStartToken)):
+            context['anchors'] = set()
+
+    if (conf['forbid-undeclared-aliases'] and
+            isinstance(token, yaml.AliasToken) and
+            token.value not in context['anchors']):
+        yield LintProblem(
+            token.start_mark.line + 1, token.start_mark.column + 1,
+            f'found undeclared alias "{token.value}"')
+
+    if (conf['forbid-duplicated-anchors'] and
+            isinstance(token, yaml.AnchorToken) and
+            token.value in context['anchors']):
+        yield LintProblem(
+            token.start_mark.line + 1, token.start_mark.column + 1,
+            f'found duplicated anchor "{token.value}"')
+
+    if conf['forbid-undeclared-aliases'] or conf['forbid-duplicated-anchors']:
+        if isinstance(token, yaml.AnchorToken):
+            context['anchors'].add(token.value)